Remove old Bookings login

I recently retired from a local college that used Microsoft Apps and Bookings. I want to add it to my business, but every time I go to log in, it takes me to my previous employer's login. How can I log out to log into my own Bookings? I was able to log out of Teams, but not Bookings. I used my work email for school, and no long have or use the old email. 

Any help would be wonderful.